Wave impact tests are performed in the LNG industry to design the structure of the cargo containment system (CCS) of the vessels and to study the physics of breaking wave impacts. The state-of-the-art methodology divides the wave impact flow into two parts: the global flow and the local flow. The global flow considered as the solution of the incompressible Euler equations for the liquid and gas in the tank; and the local flow as a perturbation of the global flow. However, researchers have found it to be a challenge to generate repeatable global flows of focused breaking waves and, therefore, to draw definitive conclusion about the contribution of the global flow variability in the impact pressure variability. In this context, a new facility was designed and built at MARIN in the framework of the SLING project to further investigate the physics of sloshing impacts: the Multiphase Wave Lab (MWL), a wave flume of 10 m in length, 0.6 m in width and water depth of 400 mm.

This thesis aimed to identify and evaluate the sources of variability of the global flow of focused waves, to define the repeatability criteria and to determine the theoretical conditions that would lead to global flow repeatability in the MWL. To achieve the objectives, both theoretical and experimental work have been required.

Three main sources of global flow variability were identified: (1) water depth variation, (2) long bounded waves (seiching) and (3) currents induced by seiching. These drivers of variability were modeled in a wave generation and propagation algorithm from which the sensitivity of the global flow to the sources of variability has been addressed. The results showed that the water depth is the most critical driver of variability and that repeatability would be achieved if its difference between experiments is below 0.5 mm.

Based on the sensitivity study and the characteristics of the wave maker, a criterion to experimentally quantify global flow repeatability was derived from the Sobolev norm of the Fourier space of free surface elevations at a distance from the focal point. To validate the theoretical value, impact waves were generated using a wave focusing technique. Linear wave and wave making theories were used to compute the paddle motion generating the wave impact of interest. The breaking wave was designed using a two-parameter Ricker amplitude spectrum formulation, which defines the contribution of each frequency to the total breaking wave energy and therefore changing its characteristics (crest thickness, crest stability, gas pocket size…). Image processing techniques were used to measure wave maker motion and free surface elevations from video recordings.

While more repetitions are required to confidently conclude about the validity of the criterion, the experimental results showed that when the ‘dissimilarity’ value was below the theoretical threshold, exceptional repeatability of the global flow was obtained.

Marine propulsion systems with diesel engines face continuous variations in propeller shaft speed and torque during operation, due to waves and changing rudder and water inflow angles. Traditional propulsion control systems do not take these variations into account, and attempt to maintain a constant shaft speed. These changing torques, in combination with inefficient control efforts, can increase mechanical wear and tear on the diesel engine, and reduce efficiency. More advanced control algorithms relying on the axial flow velocity of water through the propeller have shown great promise. Unfortunately, this velocity, also known as the advance velocity, is very difficult or impossible to measure. Therefore, it is possible to use state observers to estimate the advance velocity using available measurements of shaft speed and torque. However, the current state of the art regarding advance velocity estimation is very limited.In this paper, a complete model of a ship propulsion system is created. Several different observer structures are applied to the propulsion model to estimate the advance velocity. These include a Luenberger observer, a Shaft Kalman Filter (SKF), a Power Balance Estimator (PBE), a Measured Shaft Acceleration (MSA) observer with and without measurements of shaft acceleration, an Immersion & Invariance (I&I) observer and a Random Walk Kalman Filter (RWKF). The performance of these advance velocity observers using different observer gains is compared using several load cases. These load cases are used to assess time domain accuracy with and without measurement noise, and robustness to errors in a priori information regarding the propulsion system. The findings indicate a clear trade off between noiseless accuracy, and robustness to noise. If an observer has high observer gains, it is more accurate when no noise is present, but more sensitive to measurement noise, and vice versa. Furthermore, higher gains also lead to more robustness to errors in a priori information. The errors that lead to the most significant estimation errors were errors in the open water propeller diagrams, with errors in the shaft inertia proving to be much less significant. That being said, if accurate shaft acceleration is available, the MSA observer is most effective. If this data is unavailable or inaccurate, a choice must be made. If measurement noise robustness is paramount, the RWKF or an I&I observer with low gains is most effective. If absolute accuracy is most important, and the measured variables are virtually free of noise, an I&I observer with high gains is the best choice. The RWKF provided a very good compromise between noise robustness and noiseless accuracy, but requires a large amount of a priori information. Suggestions for future research include testing the observers in both cavitation tunnels and full scale propulsion systems, and implementing multivariable propulsion control using the estimated advance velocity.

Over the past years tugs are evolving to more compact designs equipped with large power installations. This inherently increases the risk of accidents, demanding a more reliable prediction of the tug’s dynamical behaviour in critical situations. To capture the dynamic behaviour of a tug, a time domain simulation tool has been developed and used to evaluate the tug’s safety in those critical situations. Multiple methods derived from recent studies are combined and used to establish a reliable description of the involved hydrodynamic forces and moments. Besides a sensitivity study is performed to investigate the impact of inaccurate approximations of those forces and moments. Furthermore, the sensitivity to a change in more design and operation related parameters has been investigated. Finally, the research includes a step by step validation and an evaluation of the current regulations.

Lateral acceleration is a key aspect of the vehicle response perceived by the driver. Assistance systems such as Active Rear Steering (ARS) or Torque Vectoring (TV) are developed to modify the lateral acceleration response such that the vehicle has an improved stability and an extended linear handling region. With this extended linear handling region the vehicle abruptly reaches tyre friction limitations (representing an entry into the vehicle handling limits (VHL)), this can potentially lead to dangerous situations. This thesis aims to quantify driver behaviour when being forced to drive near the VHL, in terms of how often the VHL is entered and what happens after entry. To assess this, a human factors experiment (N = 18) in a fixed base driving simulator was performed. In this experiment three different vehicle configurations were compared: (1) a conventional vehicle (Passive) (2) a vehicle with an extended linear handling region (Active) (3) a vehicle with an extended linear handling region and increased yaw response (Active Sport). In these configurations, the drivers need to drive with a fixed velocity on an oval track with Electronic Stability Control (ESC) switched off. It was expected that a conventional vehicle enters the VHL more often compared to the vehicles with an extended linear handling region. However, when entering the VHL, the vehicle with an extended linear handling region was expected to be more difficult to control due to the abrupt change in vehicle dynamics and corresponding steering feel. The results indicate that the Passive vehicle entered the VHL more frequently compared to the Active and Active Sport configurations. However, when the Active Sport configuration entered the VHL, significantly more road departures and an increased steering reversal rate compared to the Passive configuration resulted. Therefore, it can be concluded drivers enter the VHL less frequently in a vehicle with an extended linear handling region (caused by systems such as ARS or TV). However when the VHL is entered it is more difficult and dangerous for a driver to control compared to a conventional vehicle.

In this thesis the differences between the monohull and semi-submersible are investigated. For a general heavy lift crane operation and its operational profile, the difference is performance and total cost are calculated. These are used to determine the turning point, the point where the semi-submersible is more favourable for a heavy lift crane operation. The monohull has relatively low capital and operational costs, but also a lower workability. There is thus a balance that has to be investigated and compared between the two vessel types. This is done for the North Sea and West Africa, which have significantly different sea conditions.

The International Maritime Organization (IMO) issued on the 13th of April 2018 a press release titled: “UN body adopts climate change strategy for shipping”. [1] This document illustrates the commitment of the IMO to significantly reduce the emission of greenhouse gasses (GHG) from international shipping in coming decades. However, the question arises whether the ambitious goals, set out in this press release, are feasible to be met.

This aim of this thesis is to investigate the economic and technological feasibility of powering a vessel while emitting minimal greenhouse gasses in 2050. The focus will be on power plant configuration consisting of an energy storage medium and energy converter. A case study, concerning a representative ROPAX ferry built in 2050, is performed to illustrate the feasibility of using such a power plant configuration.

Energy storage media considered are hydrogen, ammonia and batteries. The use of internal combustion engines, fuel cells and an ammonia reformer are also investigated. The performance of power plant configurations with respect to their estimated greenhouse gas emission, overall weight, required volume, initial investment cost and cost of the required energy per day of operation is evaluated and based on the results of this study several conclusions are drawn.

• First and foremost is the need to reduce the price difference of hydrogen and ammonia compared to LNG. Without this reduction, no single synthetic fuel can be considered economically feasible. Three options to reduce the price difference are identified:
- a high LNG price including high emission tax;
- a low commercial electric energy price; or
- synthetic fuel production using excess renewable energy.
Especially the last of these three is considered to be a feasible measure due to the expected presence of excess energy from solar and wind farms.
• The second conclusion is that using fuel cells or batteries are the most environmentally friendly option due to the emission of N2O when using internal combustion engines.
• Thirdly, all sustainable configurations require a considerable amount of space.
• Furthermore, the combination of relative low electrical efficiencies and high hydrogen price result in high daily costs for hydrogen fueled internal combustion engines and PEMFCs.
• The initial investment cost and system weight of batteries-based configurations are high.

Following these conclusions, only three power plant configurations remain. Based on expected safety and logistical concerns and the expected potential for improvements, a single configuration was determined to be the most suitable to be used on a ROPAX ferry in 2050. This power plant configuration is composed of a SOFC directly fueled by ammonia.

After assessing the safety concerns associated with handling ammonia and the implications the established power plant configuration has on the general arrangement of the ship, it is concluded that the use of such a power plant configuration is highly likely to be feasible in 2050. However, it is recommended to perform a more in-depth analysis of required safety measures and operating characteristics of fuel cells in future research.

In recent years the awareness and the effort to reduce air pollution and global warming have increased. Many new ideas are being developed to reduce harmful emissions. Despite this, the shipping industry is still a large contributor to air pollution worldwide. To reduce the environmental impact of shipping, the use of
sustainable energy sources such as wind energy on-board ships is being explored. Wind energy is widely available at sea, the challenge is to harness this energy. The relatively unknown wind propulsion device called the Turbosail is a vertical wing shaped device which uses wind energy to provide thrust. This propulsion technology was invented in the 1980’s by the Frenchman Jacques-Yves Cousteau. This report describes the investigation into the similar wind propulsion device called the VentiFoil. Two retractable VentiFoils are fitted inside a 40 foot container, this ship propulsion device is called the eConowind unit. Multiple eConowind units can be installed on the hatch covers of general cargo vessels. If successful, this wind propulsion device can be applied on many different ships. The VentiFoil concept will be investigated and improved using Computational Fluid Dynamics (CFD) research tools. These tools are used to simulate the flow around different VentiFoil geometries. The result of this project will be a better understanding of the working principles of the VentiFoil, sensitivity information for the variation of different characteristic design parameters and an evaluation of the generated forces and performance of VentiFoil propulsion.

Currently, lower-body exoskeletons for
paraplegics are investigated as an alternative to wheelchairs
and as an exercise method with medical benefits. Literature
provides little examples for users to influence the
length or frequency of steps taken by the exoskeleton,
complicating stability and practical usability. This study
proposes a novel control paradigm that allows users to
influence step parameters of the exoskeleton, through a
bi-directional haptic interface that also provides feedback.
The exoskeleton handles the cyclic walking pattern while
the patient is enabled to correct for disturbances. I adapted
an existing lower-body exoskeleton trajectory generator to
allow real-time adaptation of step length and swing time.
To demonstrate a proof-of-concept of the control paradigm,
I implemented the controller for a virtual 2D exoskeleton,
to be controlled by an existing bi-manual haptic control
interface. A human-in-the-loop experiment was performed
with the goal to compare the benefits of user control
over either step length or swing time with a situation
with no human control. In the experiment perturbations
of increasing magnitude were applied to a 2D virtual
exoskeleton, participants could increase or decrease either
step length or swing time during swing to correct for these
disturbances. The number of successful step taken before
the perturbations resulted in a fall were measured. The
swing time group succeeded in making the exoskeleton
walk stably significantly longer then when there was no
human input, proving that the proposed control paradigm
is feasible and beneficial for stability.

Motion compensation for personnel transfer has greatly reduced costs and increased accessibility for offshore assets operation and maintenance. Solutions exist using hexapods or gangways that make a stiff connection by clamping to a customized offshore structure. State of the art gangways allow for a stepless workflow and have a rubber tip which does not require specialized landing structures. However, in these solutions contact force variations are high. This results in a reduction of safety due to the loss of contact or slipping motions. Therefore, a system with force sensors in the tip is proposed. This allows for the tip forces to be used in feedback control. Literature on this subject describes hydraulic actuator force control, impedance control, or force control in free moving robotics. Literature fails to describe suitable solutions to the hydraulic force control problem where motions are dictated and force tracking is required. In this thesis the dynamic problem of force-position control with hydraulics is simplified, allowing linear analysis and controller design. A 3D model has been created and used to show the need for force feedback after which an analysis is performed on the actuator dynamics. The root locus method is used to close the force control loop with a proportional-integral controller. This results in a complete force-position control structure which tracks a force setpoint on a moving object. The controller structure has been implemented during sea trials and showed significant improvement in the force control performance. This approach of force control using hydraulic actuation is expected to significantly increase safety in offshore operations.

At the Lion Foundation a hunting simulator is used to stimulate the hunting instincts and skills of lions and tigers, in order to improve their health and increase chances of relocation into the wild. The hunting simulator is an animal enclosure wherein a piece of meat, used as prey, is moved by means of a joystick-controlled cable-driven system. The animal caretakers find it difficult to operate the hunting simulator effectively: the position of the prey relative to the hunting cat and enclosure is hard to judge. Evading the fast unpredictable cats requires high prey velocities without crashing into obstacles or enclosure walls. In this study it is hypothesized that providing the operators with haptic assistance through the joystick will help them to improve their performance, i.e. it will allow them to navigate the prey through the enclosure at higher velocities while having fewer collisions. Haptic assistance was designed as a force-stiffness feedback algorithm based on the inverse Time-to-Collision. It was implemented on a purposefully designed virtual hunting simulator operated through a force-feedback gaming joystick. Naive subjects (n=10) participated in an experiment in which they were asked to navigate the virtual prey through a series of waypoints, without hitting the boundaries of the virtual enclosure or the obstacles within it, both with and without the designed haptic assistance. Results show that haptic assistance leads to significant benefits for the operators, as they moved significantly faster while having significantly fewer collisions. In conclusion, the designed haptic assistance is beneficial when used in the virtual hunting simulator, and therefore constitutes a promising method that warrants implementation and evaluation in the real- world hunting simulator.

The awareness of the impact of air pollution on global climate change is more and more growing in society. The urgency to make ships more eco-friendly captures the interest of shipowners and naval architects. Hull designs of a ship, with regard to minimum fuel consumption have been optimized in the last decades and it has been proven difficult to improve current hull forms. Another strategy is to reduce fuel consumption by using external wind power combined with engine power, so called 'wind-assisted propulsion' or 'motor-sailing'. The potential of an extraordinary high lifting device of a mechanical sail using aspiration power, known as a 'Turbosail' introduced by Jacques Cousteau [1], has been selected as wind propulsion for an existing cargo ship. This foil can generate about 3 times higher lift compared to conventional foils, which do not use active suction of the boundary layer. Similar to the concept of a velocity prediction program for sailing yachts, a fuel prediction program (FPP) is set up to visualize the fuel savings for all wind directions relative to the vessel. For a wind force 7 Beaufort, the fuel savings for optimal wind angle can reach up to 40%, which are enormous.

The working mechanism of the Turbosail is further explored and examined with CFD using ReFRESCO [38], to see if the performance of the Turbosail is as high as reported by Cousteau. Steady and unsteady RANS simulations are conducted for infinite span Turbosail using the k-ω SST turbulence model of Menter [32]. As a verification study, an expansion of two other turbulence models are included, which are the  k-ω SST-LCTM model of Langtry et al [30] and the EARSM model for a more anisotropic flow accounting for Reynolds stresses. The difference between all turbulence models appeared to be small, and a fair agreement is found with the lift and drag coefficients found by experiments of Cousteau.

A steady RANS simulation has been conducted at model scale for a finite Turbosail to calculate the lift, drag and aspiration power. The distribution of air suction along the span of the foil is visualized, which gives insight for the real experiments. During this study, a Turbosail at model scale 1:2 is built with a span height of 5.5 metres and a chord length of 1 metre. The comparison with CFD is therefore very useful for validation. As a final step, the lift and drag coefficients found from the numerical result are implemented in the FPP. The fuel savings from the FPP are analysed by placing four full scale Turbosails on an existing cargo ship. In this model, there has been accounted for aspiration power needed for the boundary layer suction. Hydrodynamic forces due to leeway of the hull and rudder, propeller efficiency and specific fuel oil consumption of the engine.